This invention relates broadly to thermoplastic injection molding apparatus and, more particularly, pertains to the enhancement of a commercially available injection molding machine to increase production capability.
Changes in plastics manufacturing strategies, particularly the growing emphasis on reducing in-process time and inventories, make multi-shot molding more viable and cost justifiable than single shot molding for a broader range of manufacturers. The multi-shot process allows multiple colors or materials to be sequentially injected in a single, continuous process to speed throughput, minimize production and assembly operations, improve part quality and create innovative part features. In most cases, a single injection molding machine with multiple injection units will generally cost less than an equivalent number of machines with single injection units. Likewise, a single two-color mold will usually cost less than two one-color molds. Because only a single machine operator is required for a multi-step process, there is a labor savings realized which can have major impact on payback calculations and life cycle costs. Floor space, electricity, and other utility costs are also reduced by consolidating operations on one machine. Faster inventory turns for savings on in-process inventory can be a critical factor in the decision matrix as well.
Despite their advantages, multi-shot injection molding machines are not readily available from the inventory from large press manufacturers and must often be custom built which results in several months of delay before the desired production can commence. Once the multi-shot machine is delivered and installed, the customer is locked into the particular design and location of the multiple injection units on a particular manufacturer""s machine. There is no adjustability of the injection unit along the x and y axis, nor is there any interchangeability with another press manufacturer""s machine or parts thereof.
Accordingly, it is desirable to provide an arrangement for removably mounting an injection molding unit on a commercially available injection molding machine in a manner which will produce all the advantages of a multi-shot machine without any of its drawbacks. It is also desirable to provide a universally applicable framework for marrying at least one molding unit into the existing die of a standard injection molding machine.
It is a general object of the present invention to transform a known single shot molding machine into a multi-shot molding machine.
It is one object of the present invention to provide a portable injection molding unit for expanding the flexibility of a standard injection molding machine.
It is another object of the present invention to efficiently provide a rail mounted injection molding unit which is adjustable along three axes of movement relative to a fixed injection molding machine.
It is a further object of the present invention to provide an injection molding conversion arrangement which can be adapted for use on variously manufactured injection molding machines.
It is an additional object of the present invention to provide alternative multi-shot molding without requiring a custom built injection molding machine.
In one aspect of the invention, an injection molding machine having a die is improved such that an injection molding arrangement is removably mounted to the injection molding machine and cooperates with the die thereof to increase the molding capability of the machine. The injection molding arrangement includes an injection barrel which is adjustable along three axes relative to the injection molding machine. The injection molding arrangement is transferable from the injection molding machine to another injection molding machine. The injection molding arrangement includes rail structure engageable with bearing structure enabling movement of the injection molding unit longitudinally and laterally of the injection molding machine. The injection molding arrangement is comprised of at least one injection molding unit removably mounted to the injection molding machine.
In another aspect of the invention, an injection molding apparatus includes a fixed, injection molding machine having a housing, a first injection molding unit and a die associated therewith. A portable framework is removably mounted to the molding machine housing and has at least a second injection molding unit operably aligned with the molding machine die and cooperable with the first injection molding unit. The framework includes a base plate fixed to the molding machine housing, and a pair of parallel side panels slidably mounted on the base plate and interconnected by cross member structure. The second injection molding unit is slidably mounted on the cross member structure. A first adjustment device is disposed between one of the side panels and the base plate for enabling sliding movement of the side panels, cross member structure and second injection molding unit relative to the base plate. A second adjustment device is disposed between the side panels for providing sliding movement of the second injection molding unit relative to the side panels and base plate. One of the adjustment devices provides movement longitudinally of the molding machine housing and the other of the adjustment devices provides movement laterally of the molding machine housing. A first set of linear bearings is interposed between the side panels and the base plate. A second set of linear bearings is interposed between the cross member structure and a mounting block structure of the second injection molding unit. The side panels have bottom rails defining a longitudinal set of rails. The cross member structure has top portions defining a latitudinal set of rails. The mounting block structure includes a pair of mounting blocks interconnected by a tie bar. The first adjustment device includes a longitudinal lead screw, and the second adjustment device includes a latitudinal lead screw. The second injection molding unit has an injector barrel which is adjustable along three different axes of movement relative to the molding machine housing.
In yet another aspect of the invention, there is contemplated a method of providing multi-shot molding capability in the production of plastic-based components. The method includes the steps of providing a fixed injection molding machine having a housing, a first injection molding unit and a die associated therewith; disposing a portable framework having at least a second injection molding unit upon the molding machine housing such that the second injection molding unit is operably aligned with the die in cooperation with the first injection molding unit; and removably fastening the framework to the molding machine housing.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.